1. Field of the Invention
The present invention relates generally to improvements in air-conditioning systems and more particularly to the use of an air terminal from which conditioned air is directed to the various zones being serviced by the air-conditioning system.
2. Prior Art
Present day heating and air-conditioning systems must be capable of controlling the temperature of many spaces within a building complex which have different cooling and heating requirements and characteristics. Some exterior spaces with an abundance of glass and on the shaded side of a building may require full heating capacity while those on an unshaded side or on a side predominantly exposed to the sun may require cooling. Simultaneously, interior surfaces always require cooling with the cooling requirement being governed by the number of people, amount of lighting and other sources of heat in the space involved.
Various air-conditioning systems have been used to handle this problem. One of the most inefficient systems now in wide use provides full cooling throughout the building and reheats this cold air to prevent overcooling any of the zones. While this type of system has a rather low initial cost, the inefficiency of such a system which uses energy to cool air and then energy to reheat the air is self evident. Thus, the system is very expensive to operate, and in fact, high energy cost will soon eliminate use of this design.
Another system in use utilizes a double duct terminal in which cold and warm air are mixed to provide air at the proper temperature to meet the heating or cooling requirements of a particular zone. This system has a relatively high initial cost and is also expensive to operate due to their relatively low efficiency. In this, and the previously described system, during building warm-up periods, as well as other times when heat is required to maintain a minimum temperature, as when the building is not occupied, the entire air distribution system must be operated, thus adding to the operating cost of the unit.
Another method incorporates variable volume, constant temperature air terminals which vary the quantity of air supplied to the interior zones of a building. In this system, the exterior zones are served by constant volume variable temperature terminals utilizing powered mixing boxes of the type covered by this inventor's prior U.S. Pat. No. 3,951,205. While this system is inexpensive initially and operating costs are relatively low, it envisions the use of several spaced air terminals positioned throughout the building complex which is serviced by it.